This invention relates generally to the art of optical temperature measuring, and more specifically, to electro-optic instruments for detecting and displaying temperature of an optical temperature detector.
Many particular techniques have been suggested for optically measuring the temperature of an object or an environment. A material that exhibits a change in some optical property is either applied directly to the object or made as part of a temperature probe such as a probe formed on the end of an optical fiber. One such material is a phosphor that exhibits some change in its light emission as a function of its temperature in response to appropriate radiation excitation. Measuring the decay time of a phosphor emission that after a pulse of exciting radiation, and the measurement of phosphor emission color shift as a function of temperature are two such methods that are described in U.S. Pat. No. 4,223,226--Quick et al. (1980).
Other techniques utilize varying phosphor emission intensity as a function of temperature. One form of this latter technique is described in U.S. Pat. Nos. 4,075,493--Wickersheim (1978) and 4,215,275--Wickersheim (1980), as well as co-pending patent application Ser. No. 167,691 of Wickersheim, filed July 10, 1980. These patents and application show as a preferred technique the use of a phosphor which, when excited to luminescence, emits detectable radiation within two or more distinct wavelength ranges that are optically isolatable from one another, the relative intensity of emission in these wavelength ranges varying in a known manner as a function of the temperature of the phosphor. The preferred phosphor is one that emits sharp lines of radiation upon excitation, such as those having rare earth activators. A temperature measuring system utilizing such a phosphor preferably takes the ratio of emissions within two optically separatable emission bands, and it is the ratio that is a function of the temperature of the phosphor. Ratioing eliminates many sources of error in the measurement, such as changes in the excitation source intensity or phosphor characteristics over time, or changes in the optical transmission system, such as an optical fiber, that communicates the phosphor emission to a detecting instrument.
It is a primary object of the present invention to provide an electro-optical instrument for use with a phosphor detector, particularly when the detector is provided at the end of a length of optical fiber, that converts the phosphor radiation emission to an accurate indication of the temperature of the phosphor.